System for controlling the duration of a self-clean cycle in an oven

Abstract

A method and apparatus is provided for operating a self-cleaning oven in which a gas sensor, such as for measuring concentrations of CO gas, is located remote from, yet in gas communication with, an exhaust flue of the oven. The gas sensor is located at the end of an outlet tube which extends from the exhaust flue. A sample gas flow is provided to the gas sensor through the outlet tube to isolate the sensor from the heat of the oven and a filter device is located in the outlet tube for filtering the sample gas flow. A valve may be provided at the inlet to the outlet tube. The rate of change (slope) of successive readings of gas concentrations may be used to determine when the combustion of food material is complete, in order to terminate a self-cleaning cycle. As a back up method to the gas sampling system, a count of lengths or numbers of baking cycles and broiling cycles performed since a last self-cleaning cycle can be kept, and a look up table consulted to determine a length of time required for a cleaning cycle. A display is provided to advise the user that a cleaning mode is in operation and to inform the user of the amount of time remaining in the cleaning cycle.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:  
     
       1. An oven capable of being operated in a self-cleaning cycle, comprising: 
       a cooking chamber;  
       a heating device in thermal communication with said cooking chamber;  
       an exhaust flue extending from said cooking chamber and leading to atmosphere;  
       a gas sensor being configured to have a signal output indicative of a measured concentration of a gas component during said self-cleaning cycle;  
       a countdown timer to count down the remaining cleaning cycle time;  
       a display device to provide the user with a visual display of information related to the self cleaning cycle; and  
       a heat control device operably coupled to the gas sensor, countdown timer, and display device to receive successive gas concentration signals from said gas sensor, set the countdown timer based on the gas concentration signals, display the remaining cycle time on the display device, and initiate termination of said self-cleaning cycle in response to the measured gas concentrations.  
     
     
       2. An oven according to  claim 1 , wherein the heat control device is operable to determine a rate of change between said sucessive signals and once said determined rate of change is maintained below a minimum preset rate of change value for a predetermined length of time to initiate termination of said self-cleaning cycle. 
     
     
       3. An oven according to  claim 1 , wherein said heating device is an electrical resistance element. 
     
     
       4. An oven according to  claim 1 , wherein said heating device is a gas burner. 
     
     
       5. An oven according to  claim 1 , wherein the gas component is carbon monoxide (CO) or carbon dioxide (CO 2 ). 
     
     
       6. An oven according to  claim 1 , further comprising: 
       an outlet tube having an inlet end connected with said exhaust flue and an outlet end, said gas sensor located at said outlet end of said outlet tube such that a sample gas flow is provided to said gas sensor through said outlet tube;  
       an activated carbon filter device located in said outlet tube for removing moisture and particulate matter from the sample gas flow supplied to said gas sensor.  
     
     
       7. The oven according to  claim 1 , wherein the heat control device is operable to determine the duration of the self-cleaning cycle based on the time rate of change of the concentration of the component. 
     
     
       8. The oven according to  claim 7 , wherein the component is at least one of carbon monoxide or carbon dioxide. 
     
     
       9. The oven according to  claim 1 , wherein the gas sensor output signal is a stop cycle signal indicative that the self-clean cycle is complete. 
     
     
       10. The oven according to  claim 9 , wherein the gas sensor further comprises a gas sensor controller operably coupled to the heat control device to receive concentration signals indicative of the concentration of a component of the exhaust gases, determines the completion of the self-clean cycle therefrom, and then sends the stop cycle signal to the heat control device. 
     
     
       11. The oven according to  claim 10 , wherein the gas sensor controller is operable to determine a time rate of change of successive concentration signals and once the determined rate of change is maintained below a minimum preset time rate of change value to send the stop cycle signal. 
     
     
       12. The oven according to  claim 1 , and further comprising an outlet tube in which the gas sensor is located, the outlet tube having an inlet end connected to the exhaust flue and establishing fluid communication therewith such that at least a portion of the exhaust gases flow into the outlet tube and to the gas sensor. 
     
     
       13. The oven according to  claim 12 , and further comprising a filter located within the outlet tube closer to the inlet end than the gas sensor. 
     
     
       14. The oven according to  claim 13 , wherein the filter is an activated carbon filter. 
     
     
       15. The oven according to  claim 12 , wherein at least a portion of the outlet tube is angled upwardly. 
     
     
       16. The oven according to  claim 12 , wherein the outlet tube has an outlet end and the gas sensor is located adjacent to the outlet end. 
     
     
       17. The oven according to  claim 1 , wherein the gas sensor is an infrared sensor. 
     
     
       18. An oven capable of being operated in a self-cleaning cycle, comprising: 
       a cooking chamber;  
       a heating device located in said cooking chamber;  
       an exhaust flue extending from said cooking chamber and leading to atmosphere;  
       an outlet tube having an inlet end connected with the exhaust flue and leading to an outlet communication with atmosphere;  
       a heat actuated valve for preventing a flow of gas from passing through the outlet tube during non self-cleaning oven cycles positioned near the inlet such that said inlet is closed by said heat actuated valve at all temperatures below a predetermined temperature;  
       a gas sensor located in said outlet tube for measuring gas concentration levels during said self cleaning cycle.  
     
     
       19. An oven according to  claim 18 , wherein said outlet tube comprises a tube having an inlet end and an outlet end and further having a portion having an upward angle. 
     
     
       20. An oven according to  claim 19 , wherein said outlet end of said outlet tube is located in a console of said oven, remote from cooking chamber. 
     
     
       21. An oven according to  claim 18 , wherein said gas sensor is located adjacent said outlet of said outlet tube. 
     
     
       22. An oven according to  claim 18 , wherein said gas sensor is an infrared sensor. 
     
     
       23. An oven according to  claim 18 , further comprising: 
       an activated carbon filter device located in said outlet tube for removing moisture and particulate matter from the sample gas flow supplied to said gas sensor.  
     
     
       24. An oven according to  claim 18 , wherein said heat actuated valve comprises a bimetal valve. 
     
     
       25. An oven according to  claim 18 , further comprising: 
       input controls for selecting baking, broiling or self cleaning operations in said cooking chamber;  
       a heat control device being operable to initiate said self-cleaning cycle upon receipt of input from a user, including operation of said heating device for providing heat to said cooking chamber to combust food items in said chamber and to initiate termination of said self-cleaning cycle upon a completion of a cleaning operation, said completion occurring at a time that can be determined in advance by said control device; and  
       a display device controlled by said heat control device to provide a first display to a user indicating that a self-clean cycle is in progress and a second display provided before an end of said self-cleaning cycle to indicate to a user a remaining amount of time required said self-clean cycle.  
     
     
       26. An oven according to  claim 25 , wherein said heat control device communicates with said gas sensor and receives successive gas concentration signals from said gas sensor and wherein said heat control device determines a rate of change between said successive signals and initiate termination of said self-cleaning cycle once said determined rate of change is maintained below a minimum preset rate of change value for a predetermined length of time. 
     
     
       27. An oven according to  claim 25 , wherein said heat control device includes a counter for counting the oven operation time since a last self-cleaning operation, and is operable to initiate termination of said self-cleaning cycle after passage of an amount of time based upon the amount of oven operation time since a last self-cleaning operation. 
     
     
       28. A method for controlling a self-cleaning oven having: a cooking chamber, a heating device for supplying heat into said cooking chamber, an exhaust outlet from said cooking chamber leading to atmosphere, a gas sensor communicating with said exhaust outlet for measuring a concentration of gas and having a signal output indicative of said measured concentration of gas during said self-cleaning cycle, and a heat control device for controlling and heating device, comprising: 
       accepting an input at said heat control device to begin a self-cleaning operation;  
       determining whether said gas sensor is operable;  
       if said gas sensor is determined to be operable, operating said heating device in accordance with a first algorithm based upon measured gas levels provided by said gas sensor; and  
       if said gas sensor is determined to be inoperable, operating and heating device in accordance with an algorithm not based upon measured levels.  
     
     
       29. A method according to  claim 28 , wherein said first algorithm comprises measuring successive CO levels with said gas sensor at periodic times, determining a rate of change of successive CO levels, and initiating a termination of said self-cleaning cycle once said rate of change of successive CO levels has reached at predetermined level for a predetermined length of time. 
     
     
       30. A method according to  claim 28 , wherein said second algorithm comprises maintaining a count of the duration of oven operation since a last self-cleaning cycle and conirolling said heating device to heat said oven cavity for a time period based upon the amount of oven operation time since a last self-cleaning operation.